1. Field of the Invention
The present invention relates to orthopedic prostheses and, particularly, to knee prostheses.
2. Description of the Related Art
In a natural knee joint, the meniscus is positioned between the distal end of the femur and the proximal end of the tibia to provide cushioning and support to the tibia and femur as they rotate relative to one another. Additionally, the medial side of the meniscus is more stationary than the lateral side of the meniscus, which is more flexible and/or mobile. The mobility of the lateral meniscus increases the ability of the lateral condyle of the femur to roll off of the tibial plateau during high flexion of the knee, i.e., it increases the ability of the femur to rotate into a position in which the lateral condyle is not entirely supported by the tibial plateau.
In a fixed bearing tibial prosthesis, external rotation of the femoral component against the tibial component can be limited due to the fixed nature of the prosthesis. Thus, the lateral condyle of the femur is prevented from rolling off the tibial plateau. In order to provide for articulation of the knee joint that better replicates the natural articulation of the knee joint, a mobile bearing tibial prosthesis may be used. In a mobile bearing tibial prosthesis, the entirety of the tibial bearing, including both the medial and lateral condyles, is rotatable relative to a tibial baseplate. Additionally, in some mobile bearing tibial prostheses, the tibial bearing is rotatable about a point positioned on the medial condyle of the tibial baseplate. This results in increased lateral rotation of the bearing component, which better mimics natural knee joint articulation.
Additionally, during a total knee arthroplasty, it may be necessary to resect the cruciate ligaments of the knee joint. This may result, for example, in decreased support and stability in the patient's knee joint.